The present invention relates to an electrical conductivity measuring device, and more particularly, to an electrical conductivity measuring device using the electrical conductivity and having an object to measure characteristics such as salinity or total dissolved solids (TDS), with being dipped into the object to be measured. Also, the present invention relates to the electrical conductivity measuring device having a function of informing electrode contamination, and for detecting whether or not an electrode is contaminated by the object to be measured and informing a user of the electrode contamination such that the electrode can be cleaned, thereby improving accuracy of a measured value.
In recent years, as awareness regarding the importance of management and usage of water resources increases, various management systems for pollution control and efficient usage of the water resources have been developed and applied. These water resources are managed to be used for various purposes such as drinking water or living water in an industrial site and a household.
In particular, as the general public is increasingly interested in well-being and health in recent years and also a salty food is revealed as a main factor for generating high blood pressure, interest in a salinometer measuring an amount of salt contained in a food is increasing. In general, the salinometer uses a property in which electrical conductivity is varied according to ion concentration of sodium chloride (NaCl) dissolved in the food. The salinometer calculates a salinity of corresponding measurement water such that a pair of electrodes contacts the measurement water, and then a voltage is applied to measure an amount of flowing current.
The above-described portable measuring device that is variously used for the household and the industrial site to measure characteristics of an object to be measure is being widely used. The portable measuring device may measure various characteristics by using electrical conductivity (EC) of an object to be measured and also accurately measure characteristics such as salinity, and total dissolved solids (TDS) according to the purpose thereof.
FIG. 1 is a perspective view illustrating a portable salinometer according to a related art, and FIG. 2 is a front view illustrating a sensor unit that is a main part of FIG. 1.
First, as illustrated in FIG. 1, the portable salinometer includes a bar-shaped main body 11 having a predetermined length and a sensor unit 14 provided on one side end of the main body 11. A display panel 12 for displaying all sorts of information including a measured result and an operation part 13 for operating the measuring device are provided on the main body 11, and the sensor unit 14 includes a pair of salinity sensor electrodes 15 for being dipped into the object to be measured to measure the salinity and a temperature sensor electrode 16 for measuring temperature of the object to be measured.
Here, as illustrated in FIG. 2, the salinity sensor electrodes 15 are spaced apart by a predetermined distance from each other, and the salinity is measured on the basis of a resistance value measured such that a voltage is applied to both sensor electrodes 14 in a state in which the sensor unit 14 is sufficiently dipped into the measurement water. Here, the measured salinity is displayed as a salinity value in a state in which the temperature of the measurement water, which is measured by the temperature sensor electrode 16, is calibrated to an ordinary temperature.
According to the above-described related art, the salinometer automatically measures the salinity by using electrical characteristics, i.e., resistance values, measured between the pair of salinity sensor electrodes, to simply and rapidly measure the salinity of the measurement water. However, the above-described salinometer measuring the salinity by using the electrical characteristics between the pair of sensor electrodes has a problem in which the electrical characteristics between both sensor electrodes is significantly varied when a foreign substance is attached thereto to generate great error in the salinity measured on the basis of the measured electrical characteristics.
In general, since the salinometer needs to maintain cleanliness to perform the measurement, the electrodes need to be cleaned for every usage. In particular, when an object to be measured includes a food such as a soup or a stew, a material contained in the food may be easily attached to the sensor electrode, and fine foreign material may not be visually recognized to frequently generate errors in measurement of the salinity due to the contamination of the sensor electrode by the foreign substance. The above-described error in measurement may also occur when the electrical characteristic is varied due to degradation (such as a case in which a surface of the electrode is oxidized to generate rust) of the sensor electrode according to long period usage.
Thus, in the salinometer according to the related art, the sensor electrode is periodically calibrated by using a standard solution according to variation in the electrical characteristic due to the above-described contamination of the sensor electrode, and the sensor calibration device for this is disclosed in Korean Patent Registration No. 10-1519356 (prior art documents).